1. Technical Field
The present invention relates to a display apparatus displaying an image by illuminating a display panel by light directed from a light source via a light guide plate.
2. Description of the Related Art
A display apparatus including a rectangular liquid crystal panel as an image display portion includes a backlight unit located at a back of the liquid crystal panel, and is configured to have illumination light from the backlight unit be transmitted through, and modulated by, the liquid crystal panel and thus to display an image on a front surface of the liquid crystal panel. Backlight units are roughly classified into direct-type backlight units and edge light-type backlight units. Recently, edge light-type backlight units have been in wide use from the point of view of decreasing the power consumption and reducing the thickness thereof.
An edge light-type backlight unit includes a backlight chassis having a shallow box-like shape, and a light guide plate and a light source accommodated in the backlight chassis. The light guide plate is a rectangular flat plate formed of glass or a light-transmissive resin material, and is placed on a bottom surface of the backlight chassis. The light source is attached to one side wall of the backlight chassis so as to face one side surface of the light guide plate. Light directed from the light source enters into the light guide plate from the one side surface thereof, propagates inside the light guide plate, and is output while being distributed in one wide surface of the light guide plate that is exposed to an opening of the backlight chassis.
The light guide plate is provided such that the one wide surface thereof faces a rear surface of the liquid crystal panel, and a rectangular optical sheet is located between the surfaces, facing each other, of the light guide plate and the liquid crystal panel. The optical sheet is an optical element having functions of diffusing and converging light, and light output from the light guide plate is directed toward the liquid crystal panel via the optical sheet.
The optical sheet is expandable and contractible by heat from the light source, and thus is supported at a portion of a peripheral edge thereof in a longitudinal direction so as to be allowed to be expanded and contracted. The optical sheet is supported by, for example, support pins inserted into holes provided in the portion of the peripheral edge thereof. The support pins are provided on a support portion supporting the optical sheet, on the light guide plate or the like (see, for example, WO2011/093119 (hereinafter “Patent Document 1”)). The display apparatus is configured such that when the display apparatus is used, the support pins are situated upward. With such an arrangement, the optical sheet is suspended with the weight thereof.
A display apparatus is usually used such that support pins are situated upward, but may be occasionally used at a different orientation. However, with the above-described configuration, the support pins are not situated upward when the orientation of the display apparatus is changed. In such a case, the structure for suspending the optical sheet is not well balanced. This causes the stress to be concentrated on the hole into which the support pins are inserted, and thus easily breaks the optical sheet. In addition, the support pins are easily pulled out from the holes, which may undesirably cause the optical to come off.